Understanding Terms and Jargon

Before any discussion involving these terms can take place it is essential that the word FAILURE is fully defined and understood. Unless the failed state is defined it is impossible to explain the meaning of Quality or of Reliability. There is only one definition of failure and that is:

NON-CONFORMANCE TO SOME DEFINED PERFORMANCE CRITERION

Refinements of definitions which differentiate between terms such as Defect, Malfunction, Failure, Fault and Reject are important in contract clauses and in classification and analysis of data but should not be allowed to cloud the understanding of the main parameters. The different definitions of these terms merely include and exclude failures by type, cause, degree or use. Given any specific definition of failure there is no ambiguity in the definitions of quality and reliability. Since failure is defined as departure from specification then to define different types of failure implies the existence of different performance specifications. Table 3.1 gives an indication of the classification of failures.